The present invention relates to a print data adjusting system, a print data adjusting method, and a software storage medium containing a print data adjusting program.
Recent advances in color ink-jet printer technology have made it possible to provide a high level of image definition for printed output of so-called photo-realistic image quality. In a color ink-jet printer capable of delivering such a high level of printout quality, color ink droplets are ejected to form dots of predetermined colors at desired points, thereby producing images in dot matrices. For color image printing, three primary color inks of cyan (C), magenta (M) and yellow (Y) or four color inks of cyan, magenta, yellow plus black (K) are used.
To realize photo-realistic quality, color reproducibility is of critical importance as well as fine dot formation. In the inside of a computer, colors are represented using red-green-blue (RGB) multi-level gradation data, whereas CMYK two-level gradation data is handled on a printer. Therefore, color space conversion and gradation conversion are performed for printout. Namely, in printing, CMYK two-level gradation is used while maintaining colors represented in RGB multi-level gradation on the premise that each dot is colored with specified density.
However, although color reproducibility is maintained with respect to print data on output, a volume per droplet of color ink may be different among print heads due to an instrumental error, resulting in each dot being colored with inconsistent density.
In the above-mentioned color ink-jet printer, if a volume per ink droplet ejected from its print head varies due to an instrumental error, each dot is not colored with specified density to cause a disadvantage of degradation in color reproducibility.
In order to circumvent this disadvantage, the inventors have examined an arrangement in which print data is adjusted in advance to compensate for an instrumental error and then a printing operation is performed according to the print data thus adjusted to improve color reproducibility. In this adjustment of print data, an adjustment table is used. For preparing an adjustment table, a patch pattern is printed in the entire gradation range using a reference print head which ejects each droplet of color ink in a specified reference volume, and also a patch pattern is printed in the entire gradation range using each print head having an instrumental error. Through comparison of patch patterns, error-free patch pattern combinations are determined, and thus a list of error-free patch pattern combinations, i.e., an adjustment table is created.
Although comparison of patch patterns is required, it is impracticable to compare patch patterns for all the colors to be reproduced. Therefore, the inventors have created an adjustment table for each element color. Although almost the same color reproducibility as with the reference print head has been attained in single-color printing, inconsistency has occurred in mixed-color printing.
In view of the foregoing, it is a principal object of the present invention to provide a print data adjusting system, a print data adjusting method, and a software storage medium containing a print data adjusting program for enabling accurate color reproduction regardless of an instrumental error among such parts as print heads.
For use with a printing apparatus which deposits element color recording materials in dot matrices on recording media to produce printed output of color images containing a plurality of element colors according to print data, a print data adjusting system arranged for adjusting print data to compensate for color variation due to inconsistency in quantity of recording materials used, characterized in that a predetermined degree of adjustment for compensating for inconsistency in quantity of each single color used is decreased at the time of color mixing through combinations of element colors to accomplish adjustment of print data.
In accomplishing the above-mentioned object of the present invention and according to claim 1 thereof, there is provided a print data adjusting system, for use with a printing apparatus which deposits element color recording materials in dot matrices on recording media to produce printed output of color images containing a plurality of element colors according to print data, which is capable of adjusting print data to compensate for color variation due to inconsistency in quantity of recording materials used, wherein a predetermined degree of adjustment for compensating for inconsistency in quantity of each single color used is decreased at the time of color mixing through combinations of element colors to accomplish adjustment of print data.
In the above-mentioned aspect of the present invention arranged as defined in claim 1, a predetermined degree of adjustment for compensating for inconsistency in quantity of each single color used is attained to cope with inconsistency in quantity of recording materials used due to an instrumental error among printing apparatus, and then the above degree of adjustment is decreased at the time of color mixing through combinations of element colors in order to adjust print data.
In the result of experiments conducted by the inventors, it has been revealed that a degree of adjustment preset for single-color printing is too large when it is applied to mixed-color printing. Although this phenomenon is considered to occur due to a variety of causes, it may be inferred reasonably that a degree of adjustment for each element color becomes to have an increased effect through color mixing. Therefore, reproducibility in mixed-color printing can be improved by decreasing the degree of adjustment for each element color at the time of color mixing so that it is not used intactly for mixed-color printing. In this case, a mixed-color order is given in a range of a secondary color, tertiary color and so forth. As the mixed-color order increases, an effect corresponding to the degree of adjustment for single color is decreased. It is therefore possible to enhance color reproducibility by decreasing a mixed-color order for each dot to an optimum level.
There are two major applicable techniques for decreasing a degree of adjustment at the time of color mixing. In one of these applicable techniques, an optimum degree of adjustment for each pixel is used. As a concrete example according to claim 2 of the present invention, there is provided a print data adjusting system as claimed in claim 1, which is characterized by degree-of-adjustment memory unit for storing a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color, degree-of-adjustment regulating unit for judging a mixed-color order for each dot and regulating the degree of adjustment to decrease to a level lower than in single-color printing when the mixed-color order becomes higher, and first adjustment unit for adjusting print data according to the degree of adjustment thus regulated.
In the above-mentioned aspect of the present invention arranged as defined in claim 2, the degree-of-adjustment memory unit stores a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color to cope with inconsistency in quantity of recording material used due to an instrumental error among printing apparatus, and the degree-of-adjustment regulating unit judges a mixed-color order for each dot and decreases the degree of adjustment to a level lower than in single-color printing when the mixed-color order becomes higher. Then, the first adjustment unit adjusts print data according to the degree of adjustment thus regulated.
It is just required for the degree-of-adjustment memory unit to store a predetermined degree of adjustment so that inconsistency in quantity of recording material used for each element color can be compensated for, and degree-of-adjustment provision is implementable in a variety of embodiments. For instance, on the premise that gradation print data is used, a conversion table may be provided for storing conversion data corresponding to each gradation level, or operation parameters may be stored as functions for performing calculation on input of gradation print data. Still more, a merged or compressed form of conversion data may stored instead of individual data items or parameters.
It is just required for the degree-of-adjustment regulating unit to judge a mixed-color order for each dot and decrease the degree of adjustment, and a diversity of techniques are applicable to implementation of mixed-color order judgment. As an example according to claim 3 of the present invention, there is provided a print data adjusting system as claimed in claim 2, wherein the degree-of-adjustment regulating unit is arranged to judge variation in compositional quantity of each element color and recognize that a mixed-color order has the highest value in case of uniform distribution.
In the above-mentioned aspect of the present invention arranged as defined in claim 3, the degree-of-adjustment regulating unit judges variation in compositional quantity of each element color. If respective element colors are almost equal in compositional quantity, they are mixed in a ratio of equivalent values. In this case, it is therefore judged that a mixed-color order is high. For color mixing, if the compositional quantities of other element colors are smaller than that of a certain element color, it is reasonably judged that a mixed-color order is low because of a decrease in the effect of a degree of adjustment. Therefore, in case of uniform distribution in compositional quantities of respective element colors, the highest mixed-color order is recognized through judgment.
A variety of techniques are applicable to determination of variation in compositional quantity of each element color, and it is not necessarily required to adopt a specific approach. As an example of a simplified technique according to claim 4 of the present invention, there is provided a print data adjusting system as claimed in claim 3, wherein the degree-of-adjustment regulating unit is arranged to judge variation in compositional quantity of each element color in accordance with a ratio of the lowest level of compositional quantity of each element color to an average value of compositional quantities of respective element colors.
In the above-mentioned aspect of the present invention arranged as defined in claim 4, the degree-of-adjustment regulating unit determines a ratio of the lowest level of compositional quantity of each element color to an average value of compositional quantities of respective element colors. In principle, a value of ratio is determined by the degree-of-adjustment regulating unit. If there are three element colors, the degree-of-adjustment regulating unit determines a ratio of three times the lowest value to a total value of these colors. Based on the ratio thus attained, a judgment is formed on variation in compositional quantity of each element color.
As to judgment on a mixed-color order by the degree-of-adjustment regulating unit, it is not necessarily required to use compositional quantity. According to claim 5 of the present invention, there is provided a print data adjusting system as claimed in claim 2, wherein the degree-of-adjustment regulating unit is arranged to judge saturation and recognize that a mixed-color order is high if saturation is low.
In the above-mentioned aspect of the present invention arranged as defined in claim 5, the degree-of-adjustment regulating unit judges saturation which has a property analogous to compositional quantity with respect to variability. In most cases, element colors are uniform when saturation is low, and a difference among element colors is large when saturation is high. Therefore, in a situation where saturation can be judged readily, judgment on saturation is applicable as a technique for determining a mixed-color order.
As to determination of a degree of regulation by the degree-of-adjustment regulating unit for decreasing a degree of adjustment for each dot, an arbitrary point of time for determining a degree of regulation may be taken. As an example according to claim 6 of the present invention, there is provided a print data adjusting system as claimed in any one of claims 2 to 5, wherein the degree-of-adjustment regulating unit is arranged to judge a mixed-color order per dot of print data and determine a degree of regulation for each degree of adjustment.
In the above-mentioned aspect of the present invention arranged as defined in claim 6, when each dot of print data is input, the degree-of-adjustment regulating unit judges a mixed-color order and determines a degree of regulation for each degree of adjustment. If print data is input in any unit other than dot, a judgment may be formed on a basis of such a unit of input data. Namely, a degree of adjustment is regulated according to the input flow of print data.
In contrast, as another example according to claim 7 of the present invention, there is provided a print data adjusting system as claimed in any one of claims 2 to 5, wherein the degree-of-adjustment regulating unit is arranged to determine, a degree of regulation in advance for each degree of adjustment in accordance with combinations of respective element colors.
In the above-mentioned aspect of the present invention arranged as defined in claim 7, the degree-of-adjustment regulating unit determines a degree of regulation in advance for each degree of adjustment according to combinations of respective element colors. The degree-of-regulation data thus determined in advance may be provided in a conversion table. If any other conversion table such as a color conversion table is available, the degree-of-regulation data may be incorporated in it so that color conversion and adjustment will be executable through single table reference.
In the other applicable technique for decreasing a degree of adjustment at the time of color mixing, a degree of adjustment for the entire print data is used. As a concrete example according to claim 8 of the present invention, there is provided a print data adjusting system as claimed in claim 1, which is characterized by second adjustment unit for adjusting print data in accordance with a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color, and degree-of-adjustment reducing unit for decreasing the degree of adjustment effected by the second adjustment unit to a level lower than in single-color printing at the time of color mixing through combinations of element colors.
In the above-mentioned aspect of the present invention arranged as defined in claim 8, the second adjustment unit adjusts print data in accordance with a predetermined degree of adjustment for compensating for quantity of recording material used for each element color, and according to the print data thus adjusted; the printing apparatus deposits element color recording materials in dot matrices on recording media to produce printed output of color images containing a plurality of element colors. In mixed-color printing through combinations of element colors, the degree-of-adjustment reducing unit decreases the degree of adjustment effected by the second adjustment unit to a level lower than in single-color printing.
In the result of experiments conducted by the inventors, it has been found that a degree of adjustment preset for single-color printing is too large when it is applied to mixed-color printing. Although this phenomenon is considered to occur due to a variety of causes, it may be inferred reasonably that a degree of adjustment for each element color becomes to have an increased effect through color mixing. Therefore, reproducibility in mixed-color printing can be improved by decreasing the degree of adjustment for each element color at the time of color mixing so that it is not used intactly for mixed-color printing.
The second adjustment unit is provided with at least single-color degree-of-adjustment data for each element color, and according to an instruction given by the degree-of-adjustment reducing unit, a degree of adjustment for each element color is decreased to adjust print data. Each print data may be adjusted individually, or if a conversion table to be referenced for print data is available, the contents of the conversion table maybe adjusted globally in advance so that color conversion and adjustment will be carried out by referencing the conversion table in each case.
It is just required for the degree-of-adjustment reducing unit to resultantly decrease a degree of adjustment effected by the second adjustment unit to a level lower than in single-color printing at the time of color mixing, and a degree of reduction is not uniform among respective cases. As an example according to claim 9 of the present invention, there is provided a print data adjusting system as claimed in claim 8, wherein the degree-of-adjustment reducing unit is arranged to decrease each degree of adjustment as the number of mixed colors increases.
In the above-mentioned aspect of the present invention arranged as defined in claim 9, the degree-of-adjustment reducing unit decreases a degree of adjustment as the number of mixed colors is increased.
If single-color adjustment setting is used for mixed-color printing, inconsistency takes place since a degree of adjustment for single-color printing is too large for mixed-color printing. Based on this principle, it is advantageous to decrease a degree of adjustment with an increase in the number of mixed colors.
In reduction of a degree of adjustment, the approach mentioned above is to be taken. Actually, however, there are situations including single-color printing and mixed-color printing in various numbers of colors. Therefore, a conditioning operation is required when determining a degree of adjustment. As a preferable example according to claim 10 of the present invention, there is provided a print data adjusting system as claimed in claim 8 or 9, wherein the degree-of-adjustment reducing unit includes degree-of-reduction memory unit for storing an optimum degree of reduction for a particular number of mixed colors and degree-of-reduction weighted addition unit for counting the number of mixed color pixels and performing addition on each degree, of reduction using a weight value corresponding to the number of pixels.
In the above-mentioned aspect of the present invention arranged as defined in claim 10, the degree-of-reduction memory unit stores an optimum degree of reduction for a particular number of mixed colors, and the degree-of-reduction weighted addition unit counts the number of mixed color pixels and performs addition on each degree of reduction-using a weight value corresponding to the number of pixels.
Accordingly, for each number of mixed colors, an optimum degree of reduction is added with a weight value corresponding to a pixel count ratio, thereby making it possible to provide a suitable degree of reduction in terms of the entire printed output.
In implementation of the above-mentioned technique for reducing a degree of adjustment preset for each element color at the time of color mixing, it is not necessarily required to use a substantial apparatus. As an example according to claim 11 of the present invention, there is provided a method of adjusting print data, for use with a printing apparatus which deposits element color recording materials in dot matrices on recording media to produce printed output of color images containing a plurality of element colors according to print data, which is characterized in that a predetermined degree of adjustment for compensating for inconsistency in quantity of each single color used is decreased at the time of color mixing through combinations of element colors to accomplish adjustment of print data.
In attaining an optimum degree of adjustment for each pixel and according to claim 12 of the present invention, there is provided a method of adjusting print data as claimed in claim 11, wherein a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color is stored, a mixed-color order for each dot is judged, the degree of adjustment is regulated to decrease to a level lower than in single-color printing when the mixed-color order becomes higher, and print data is adjusted in accordance with the degree of adjustment thus regulated.
Further, in attaining a suitable degree of adjustment in terms of the entire printed output and according to claim 13 of the present invention, there is provided a method of adjusting print data as claimed in claim 11, wherein a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color is set up, and the degree of adjustment is decreased to a level lower than in single-color printing at the time of color mixing through combinations of element colors to accomplish adjustment of print data.
Namely, it is not necessarily required to use a substantial apparatus for adjustment of print data, and a method of adjusting print data as mentioned above may be used.
As set forth above, a print data adjusting system arranged to adjust print data may be provided discretely, or it may be incorporated in a certain apparatus. It is to be understood that the essential concept of the present invention covers a variety of embodiments, and there may be provided a print data adjusting system.implemented in hardware or software.
Where the present invention is implemented in a form of color adjusting software as an exemplary embodiment of the essential concept thereof, it is obvious that a software storage medium may be used for containing the color adjusting software.
As an example according to claim 14 of the present invention, there is provided a software storage medium containing a print data adjusting program, for use with a printing apparatus which deposits element dolor recording materials in dot matrices on recording media to produce printed output of color images containing a plurality of element colors according to print data, which is capable of adjusting print data to compensate for color variation due to inconsistency in quantity of recording materials used, wherein a predetermined degree of adjustment for compensating for inconsistency in quantity of each single color used is decreased at the time of color mixing through combinations of element colors to accomplish adjustment of print data.
In attaining an optimum degree of adjustment for each pixel and according to claim 15 of the present invention, there is provided a software storage medium containing a print data adjusting program as claimed in claim 14, wherein a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color is stored, a mixed-color order for each dot is judged, the degree of adjustment is regulated to decrease to a level lower than in single-color printing when the mixed-color order becomes higher, and print data is adjusted in accordance with the degree of adjustment thus regulated.
Further, in attaining a suitable degree of adjustment in terms of the entire printed output and according to claim 16 of the present invention, there is provided a software storage medium containing a print data adjusting program as claimed in claim 14, wherein a predetermined degree of adjustment for compensating for inconsistency in quantity of recording material used for each element color is set up, and the degree of adjustment is decreased to a level lower than in single-color printing at the time of color mixing through combinations of element colors to accomplish adjustment of print data.
It is to be understood that a software storage medium for holding the print data adjusting program may be a magnetic storage medium, a magneto-optical storage medium or any software storage medium to be developed in the future. Obviously, the print data adjusting program according to the present invention may take such a replicated form as a primary replicated product, secondary replicated product, etc. In addition, the print data adjusting program according to the present invention may be supplied through use of a communication line or in a form of contents written in a semiconductor chip.
Still more, in view of the essential concept of the present invention, there may be provided such an arrangement that some parts of the present invention are embodied in software while the other parts thereof are embodied in hardware. In a modified embodiment of the present invention, some parts thereof may be formed as software recorded on a storage medium to be read into hardware as required.
As mentioned hereinabove, the present invention provides a print data adjusting system which is capable of eliminating color variation due to an instrumental error among printing apparatus by reducing a degree of adjustment at the time of color mixing, thereby improving color reproducibility.
Further, according to claim 2 of the present invention, a degree of adjustment is set up for each element color, thereby eliminating difficulty in determining a degree of adjustment for color mixing.
Moreover, according to claim 3 of the present invention, a mixed-color order is determined by making reference to compositional quantity of each element color and it is therefore possible to judge the number of mixed colors and a degree of effect thereof, enabling improvement in color reproducibility.
Still more, according to claim 4 of the present invention, variation in compositional quantity of each element color can be figured out through relatively simple calculation.
Furthermore, according to claim 5 of the present invention, a mixed-color order is determined using saturation which is one of characteristics in color reproduction, thereby providing suitability in a situation where saturation is evaluated for any other purpose.
Still further, according to claim 6 of the present invention, a degree of regulation is determined for each dot and calculation is performed only for necessary colors, i.e., there is no need for determining a degree of regulation as to unused colors. In particular, the amount of calculation can be reduced by caching the result thereof.
Moreover, according to claim 7 of the present invention, a degree of regulation is determined in advance and a conversion table is prepared. Thereafter, it is just required to make reference to the conversion table, and if the conversion table is incorporated in any other conversion table, the number of reference sequences can be reduced in total.
Still more, according to claim 8 of the present invention, since a degree of adjustment is set up for each element color, it is possible to obviate difficulty in determining a degree of adjustment for color mixing.
Furthermore, according to claim 9 of the present invention, a degree of adjustment is decreased as the number of mixed colors is increased. Thus, a degree of adjustment for each single color is reduced in color mixing, realizing satisfactory color reproducibility.
Still further, according to claim 10 of the present invention, the number of mixed color pixels is counted and addition is performed on each degree of reduction using an optimum weight value, thereby making it possible to determine a degree of reduction which is suitable for the entire printed output.
Besides, according to claims 11 to 13 of the present invention, a method of adjusting print data can be provided for enhancing color reproducibility in mixed-color printing similarly.
In addition, according to claims 14 to 16 of the present invention, it is possible to provide a software storage medium containing a print data adjusting program capable of enhancing color reproducibility in mixed-color printing.